Surgical resection of malignant tumors is the single most effective therapy for cancer. Long-term patient outcomes are strongly determined by the extent to which the surgeon can completely remove all diseased tissues. Present cancer imaging and detection methods often fail to provide a clear picture of the extent of disease. SPECT (single photon emission computed tomography) is a sizeable market with a large installed base of scanners. SPECT has not adequately been supported for use in cancer imaging. Recent developments SPECT/CT fused imaging technology with attenuation correction alter this picture. Enlyton proposes to develop and test a series of tunable antibody targeting compounds for SPECT imaging of adenocarcinoma (e.g., colorectal, pancreatic, gastric, esophageal, lung) in cancer patients. It is an aim of this proposal to construct specific antibody targeting compositions that can rapidly accumulate in tumors while clearing from circulation quickly. It is a further aim to validate in vivo the efficacy of the preferred single chain antibody configuration, and optimize the time to SPECT/CT imaging. The modified tumor targeting agent will be labeled with an appropriate radioisotope (123I) to enable dosing and imaging within 24 hours using existing SPECT and SPECT/CT imaging platforms.